Electrical tuning device



A. P. BOCK ELECTRICAL TUNING DEVICE July 13, 1943.

Filed Nov. 29, 1941 2 Sheets-Sheet l INVENTOR 65/7 My Ffioc/i.

ATTORNEY ITNESSES:

July 13, 1943. A. P. BOCK ELECTRICAL TUNING DEVICE Filed Nov. 29, 1941 2 Sheets-Sheet 2 INVENTOR flfi/r/ey P 500/ WITNESSES: AVM

ATTORNEY Patented July 13, 1943 ELECTRICAL TUNING DEVICE Ashley P. Biock C atonsville, Md, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 29, 1941, Serial No. 421,081

7 Claims.

This invention relates to variable tuning devices, and more particularly to inductance coils of the type utilizing rigid helical windings and moving contactors in cooperation therewith to vary the eifective inductance.

An object of the invention is to improve the mechanical structure of tuning devices of the above type, and particularly to reduce the losses at high frequencies.

A particular feature of the tuning device constructed in accordance with the invention is that the contactor mechanism while providing a firm electrical bond between the stationary and the movable portions, is nevertheless easily adjustable With the minimum of force. This feature is particularly advantageous for large tuning units of radio transmitters operating at 50 kw. or higher power.

One of the advantages residing in the mechanical construction of the variable inductance coil is that all sliding contacts are of the rolling type, whereby friction is reduced to a minimum. At the same time the construction of the rollers permits the use of the entire available surface for electrical as well as mechanical contact.

Other features and advantages will be apparent from the following description of the invention, pointed out particularly in the appended claims and taken in connection with the accompanying drawings, in which:

Figure l is a side elevational View in partial cross section of the variable inductance,

2 is a front elevational view substantially along lines A-A of Fig. l, and

Fig. 3 is a bottom view of the portion showing the contact wheels and the assembly of the sliding member of Fig. 1.

Referring to the figures, the tuning device comprises a support formed by a front ring plate l and a back ring plate 2. These ring plates are cut as seen in Fig. 2 so as not to form a complete metallic structure. An insulation portion 3 is inserted to maintain a rigid mechanical In this manner, current circulation due to induction in the ring plates forming the frame of the entire coil is prevented and electrical losses reduced. The coil frame is completed by the cross bars 4 fastened to the ring plates I and 2 of suitable insulating material which are grooved also to receive the helical conductor. The helix is formed by the conductor 5 generally of tubular copper so wound that each turn fits into the spaced grooves of the cross bars 4. A square shaft 6 runs longitudinally and coincident with the axis of the coil. The shaft 6 at one end has a round portion 1 which rotates in bearings 8 supported by the end plate 9. The latter is mounted diametrically on the ring plate A wheel ill is secured to the protruding portion 1 5 of the shaft 5 for rotating th latter by suitable mechanical coupling. The other end of the shaft 6 is also rounded and rotates in bearing ll supported by the end plate 9 which is mounted on the ring plate 2. A sliding member composed of a ring 52 of insulating material and bracket l3 surrounds the shaft 8 and is adapted to be moved ccaxially with the coil. The mechanical alignment of the sliding member is obtained by means of the wheels i l, two of which are held by the spring member l5 fastened to the bracket l3 by means of screws l6. Diagonally opposite to wheels across the shaft 6 are wheels M held by the spring member i5 secured to the bracket i3 by the screw lb". The wheels [4 and i4 are cut with a 90 angle groove which coincides with the edge formed by adjacent sides of the shaft 6. I this manner, the grooves hold the sliding member firmly against the shaft 6 preventing rotation of the member around the shaft, at the same time longitudinal motion is made easy along the edges of the shaft. In the front elevational cross section of Fig. 2, the action of the rollers l4 and id is particularly well illustrated showing that the grooved wheels on opposite ends grip the shaft on four sides. The bearings for the wheels are held by the U-shapcd members I23 and I8 which are riveted to the respective spring members i5 and it. The construction of the bracket l3 can be seen in Fig. 2 forming a horseshoe on the ring Th" latter as stated before, is of insulating material which is indicated by the small cut cross-sectioned to show the insulation. The bracket holds not only the rollers riding on the shaft 5 but also one or" the contactor assemblies 25, the latter comprising the inner telescoping member 2i and the outer member 22. A ilar contactor 25 is placed in radial opposition and is constructed similarly. It is cross sectioned w the telescoping portions and the spring applies pressure to the outs-1r telescoplbcr The latter carries the contactoi -1 which is so grooved as seen in Fig. l, as y the cylindrical curvature of the on wh ch it rides due to the presby the spring 23. The contactors unted on the bracket 5 and, thereetallic o question betwe-m the eieby and the shaft 5 t ro gh and i l. To uro an even greater electrical contact, a flexible electrical connection 26 is provided between the telescoping member 22 and the bracket IS. The second contactor 25 on the other hand is mounted directly on the insulating ring I2 by means of the bracket 21. The function of this contactor will be better understood when describing the operation of the tuning device. While the second contactor does not function as an electrical contacting device, it is important for the smooth riding of the entire contact assembly over the shaft 5 and alongside the convolutions of the conductor 5.

When the tuning device is used as a variable inductance, connection may be made to the conductor 5 at the start of the turn or in most cases the conductor 5 simply extends before starting its helical convolutions. Connection may be made directly to the extended portion, or at several places along the outer periphery of the conductor as long as the connections clear the riding surface of the contactor rollers 24. The other terminal is the revolving shaft 6 which may carry a riding contact as shown in Fig. 1 by the spring member 29 which presses firmly against the end of the shaft 6. Other types of connections which maintain direct contact with the shaft 6 may be used depending upon the type of circuit to which the tuning device will be connected. In certain cases a connection to the spring member 2.9 is made from the end turn of the conductor 5, thereby grounding the end of the coil. If it is desired that the shaft 6 be above ground potential, the end plates 9 and 9' in which it is journalled may be made of suitable insulating material. Exerting rotary motion to the shaft 6 by means of the wheel l0 will cause the rotation of the sliding member with the shaft, since the wheels l4 and M are held rigidly to the edges and sides of the shaft 6 and the grooves therein will not allow slippage. Consequently, the rollers 24 will travel over the inner surface of the conductor and guided by the convolutions thereof will follow turn for turn. As the rollers 24 glide along the conductor 5, the wheels l4 and I4 travel lengthwise along the shaft depending on what direction the shaft is turned. The force which moves the sliding member is exerted by the contactors and 25 simultaneously, and in the same direction. If one of the contactors, that is, the one which is insulated from the shaft 6, is omitted, the force exerted by the other contactor would tend to displace the wheels Hi and [4' in a direction perpendicular to their line of travel. The displacing action of this force is, therefore, counteracted by the second contactor 25 which then acts as a guide in assuring a second force acting in opposition to the one which one contactor alone would exert. The guiding action of the second contactor, therefore, maintains the sliding member substantially parallel with respect to the shaft 6.

I claim as my invention:

1. A variable inductance coil comprising a helically wound conductor, a rotatable shaft of polygonal cross-section positioned coaxially within said coil, a sliding member surrounding said shaft including a plurality of grooved contact wheels, said wheels being so disposed with respect to said shaft that the angle formed by said grooves substantially coincides with the angle formed by adjacent sides of said shaft guiding said wheels longitudinally along the edges formed by said sides but preventing rotation of said sliding member around said shaft, means carried by said sliding member for maintaining said wheels in engagement with said shaft, a pair of radially extending contactors carried by said sliding member, said contactors, terminating in contact wheels engaging said conductor, and means for rotating said shaft.

2. A variable inductance coil comprising a helically wound conductor, a rotatable shaft positioned coaxially within said coil, a sliding member surrounding said shaft including a plurality of grooved contact wheels, said wheels being so disposed with respect to said shaft that the angle formed by said grooves substantially coincides with the angle formed by adjacent sides of said shaft guiding said wheels longitudinally along the edges formed by said sides but preventing rotation of said sliding member around said shaft, spring means carried by said sliding member for maintaining said wheels in engagement with said shaft, a pair of radially extending contactors carried by said sliding member, said contactors terminating in contact wheels engaging said conductor, means for rotating said shaft, and an electrical connection between one of said contactors and said contact wheels engaging said shaft.

3. A variable inductance coil comprising a helically wound conductor, a rotatable shaft positioned coaxially within said coil, a sliding member surrounding said shaft including a plurality of grooved contact wheels, said wheels being so disposed with respect to said shaft that the angle formed by said grooves substantially coincides with the angle formed by adjacent sides of said shaft guiding said wheels longitudinally along the edges formed by said sides but preventing rotation of said sliding member around said shaft, spring means carried by said sliding member for maintaining said wheels in engagement with said shaft, a pair of radially extending contactors carried by said sliding member, said contactors terminating in contact wheels engaging said conductor, means for rotating said shaft, an electrical connection between one of said contactors and said contact wheels engaging said shaft, said contactors being radially opposite and spaced apart axially with respect to said coil whereby said contact wheels engaging adjacent turns of said coil maintaining said sliding member substantially parallel with respect to said bar.

4. A variable inductance coil comprising a helically wound conductor, a rotatable shaft positioned coaxially within said coil, a sliding member surrounding said shaft including a plurality of grooved contact wheels, said wheels being so disposed with respect to said shaft that the angle formed by said grooves substantially coincides with the angle formed by adjacent sides of said shaft guiding said wheels longitudinally along the edges formed by said sides but preventing rotation of said sliding member around said shaft, spring means carried by said sliding member for maintaining said wheels in engagement with said shaft, a pair of radially extending contactors carried by said sliding member, said contactors terminating in contact wheels engaging said conductor, means for rotating said shaft, an electrical connection between one of said contactors and said contact wheels engaging said shaft, said other contactor being electrically insulated from said shaft.

5. A variable inductance coil in accordance with claim 2, wherein said contactors comprise a pair of telescoping members and spring means within said members applying pressure in the radial sense with respect to said shaft, one of said telescoping members being mounted upon said sliding member and the other carrying a contact wheel engaging the inner surface of said helical conductor.

6. A variable inductance coil in accordance With claim 2, wherein said sliding member includes an insulated ring support around said shaft, said support carrying a plate member having radially extending portions, a pair of said spring members being mounted upon said plate member and extending axially at each end carrying a grooved Wheel, one of said contactors being mounted upon said plate member and the other directly upon said ring.

7. A variable inductance coil comprising a helically wound conductor, a rotatable shaft of polygonal cross-section positioned coaxially within said coil, a sliding member surrounding said shaft including a plurality of grooved contact wheels, said Wheels being so disposed with respect to said shaft that the angle formed by said grooves substantially coincides With the angle formed by adjacent sides of said shaft guiding said wheels longitudinally along the edges formed by said sides but preventing rotation of said sliding member around said shaft, means carried by said sliding member for maintaining said Wheels in engagement with said shaft, a pair of radially extending contactors carried by said sliding memher, and means for rotating said shaft.

ASHLEY P. BOCK. 

